The present invention generally relates to apparatus for size reduction of material pieces and, more specifically, to an apparatus for fine grinding operations used to reduce material, such as rubber, wood, plastic or other materials, into a fine powdered form.
The present invention generally relates to improvements on the apparatus disclosed and claimed in U.S. Pat. No. 5,509,610 (the ""610 patent), the disclosure of which is hereby fully incorporated by reference herein. The apparatus disclosed in the ""610 patent may be converted from a centrifugal chopping apparatus to a centrifugal grinding apparatus to reduce particulate material in stages to smaller and smaller particulates. Often, different machines and operations are necessary in order to reduce large objects, such as waste automotive tires, into useful recyclable powered form. Two other examples of apparatus for shredding waste automotive tires are disclosed in U.S. Pat. Nos. 4,684,071 and 4,927,088.
Such apparatus as disclosed in U.S. Pat. Nos. 4,684,071 and 4,927,088, and other similar devices, are incapable or at least very inefficient at reducing tires into the fine, powered form necessary for recycling or other constructive uses of the rubber material. For example, finely powered rubber may be added to asphalt for paving roads and highways or may be recycled and formed into various rubber containing products. Therefore, it is very important from an environmental standpoint to further increase the efficiency of reducing waste automotive tires to the most useful form, i.e., a powered form, in order to take these waste tires completely out of landfills and recommit their materials of construction to many useful purposes.
Reducing waste automotive tires, and other materials, down to a size of about xc2xc inch to xe2x85x9c inch pieces has not been a significant problem in the past. However, the costs associated with the manufacture, operation and maintenance of past grinding machines or size reduction machines capable of grinding or milling these pieces down to, for example, xe2x88x9240 mesh to about 100 mesh is quite high. For example, the costs associated with manufacturing minute openings in the screens used in typical hammer mills and granulators are especially high when considering that the screens must be constantly replaced. The present invention provides even further improvements to the fine grinding abilities of the apparatus disclosed in the ""610 patent.
It would also be desirable to address other problems with past methods and apparatus for producing minute particle sizes, including improvements related to more efficient and inexpensive manners of setting up and maintaining the apparatus in an optimum grinding configuration.
The present invention generally provides a centrifugal grinding apparatus especially useful for fine grinding or milling operations. The apparatus generally includes a housing having an inlet and an outlet. A first disc or plate is secured within the housing and includes a first inclined surface and a plurality of generally radially extending cutting elements. Each of the first plurality of generally radially extending cutting elements define a first serrated edge extending above the first inclined surface. A second disc or plate is mounted within the housing and includes a second inclined surface and a second plurality of generally radially extending cutting elements. Each of the second plurality of generally radially extending cutting elements defines a second serrated edge extending above the second inclined surface and intermeshing with the first serrated edge. The first and second inclined surfaces oppose one another and define a grinding space therebetween that gradually becomes more narrow in a radially outward direction relative to the centers of each plate. At least one of the first and second plates is mounted for rotation within the housing and a drive is operatively coupled to the one plate for rotating same during a grinding operation.
Each of the radially extending cutting elements of the first and second pluralities of generally radially extending cutting elements further includes a plurality of multi-sided blade elements retained on an elongate support member. The multi-sided blade elements each have at least three sides with each side defining a cutting edge and each blade element is retained on the elongate support member in a manner allowing rotation thereof to select different cutting edges thereon to define a corresponding one of the serrated edges. At least some of the multi-sided blade elements have four sides with each side defining one of the cutting edges. A shearing space is defined between the first and second serrated edges and the shearing space also becomes gradually more narrow in a radially outward direction. The inlet is defined at a radially inward location, and preferably a central location of a stationary one of the plates and the outlet is disposed at a radially outward position, preferably at the periphery of the plates such that grinding takes place as the particulate material moves from the radially inward inlet toward the radially outward outlet through the gradually narrowing spaces between the two plates and serrated edges of the cutting elements.
As another feature, at least three adjustment pads are positioned adjacent one of the first and second plates and engage another set of pads adjacent the other plate during the grinding operation. The engagement of these two sets of pads defines the size of the shearing space between the first and second serrated edges. The three adjustment pads are movable, such as through a threaded rotating action, toward and away from the three pads adjacent the other one of the first and second plates. Once the three movable adjustment pads are moved to the desired position they may be locked in place relative to the other three pads to define the size of the shearing space.
Various additional features, objectives and advantages of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description of the preferred embodiment, taken in conjunction with the the accompanying drawings.